Sceloporus hesperus, Bryson & Grummer & Connors & Tirpak & Mccormack & Klicka, 2021

Bryson, Robert W., Grummer, Jared A., Connors, Elizabeth M., Tirpak, Joseph, Mccormack, John E. & Klicka, John, 2021, Cryptic diversity across the Trans-Mexican Volcanic Belt of Mexico in the montane bunchgrass lizard Sceloporus subniger (Squamata: Phrynosomatidae), Zootaxa 4963 (2), pp. 335-353 : 348-350

Sceloporus hesperus sp. nov. Bryson & Grummer

Figs. 6–7 , Tables 3–4

Holotype: Adult male, MZFC 35571 (field number RWB 1107), from 2.2 km (by air) SE Lago de Juanacatlán, Sierra de Mascota , municipality of Mascota , Jalisco (N 20.6102°, W 104.7208°, 2314 m; WGS84); collected 10 April 2011 by R. W. Bryson Jr. and M. Torocco.

Paratypes: Same data as holotype ( MZFC 35572–35575 ) .

Diagnosis. Sceloporus hesperus is a member of the S. scalaris group, sharing with other species in that group parallel lateral scale rows, femoral pore series that are either in contact or separated by no more than two scales, females with smooth preanal scales, and males with lateral abdominal color patches ( Smith 1939; Smith et al. 1997; Watkins-Cowell et al. 2006). Sceloporus hesperus can be distinguished from other species in this group by the following combination of characters: single canthal on each side of the head, small adult size (SVL less than 47 mm, average 45.4 mm), 41–47 dorsal scales (average 43), 40–45 scales around midbody (average 43), 37–39 ventral scales (average 38), tibia length/head length proportion of 0.75–0.89 (average 0.84), 11–17 scales bordering the interpariatel scale (average 14), adult females with lightly mottled or pale venters, and adult males with extensive dark pigment on the venter, heavily mottled throats, and orange or rust-colored flanks.

Description of holotype. Adult male ( Fig. 6 ). SVL = 43 mm, total length including tail = 112 mm. Head length = 9.64 mm. Tibia length = 8 mm. Entire hind limb length (including fourth toe) = 21 mm. Forelimb length = 11 mm. Dorsal head scales keeled with smooth margins. Four internasal scales, two deeply notched towards midline and two rectangular. Canthals 1-1. Loreals 1-1. Supralabials 5-4. Infralabials 6-6. Postnasals 2-3. Preoculars 1-1 with strong transverse keel on dorsal surface. Three frontonasals, each with many ridges. Three prefrontals, each with many ridges. Frontal trapezoidal, with three ridges. Frontoparietals 1-1. Parietals 2-1. Lorilabial rows 2-2. Dorsal scales keeled, triangular, with sharp posterior point. Dorsal scale margins transparent, smooth (not serrate). Forty two dorsal scales. Forty scales around midbody. Ventral scales rounded, with a notch at posterior apex.

Two white dorsolateral stripes, one-scale wide, that begin at posterior margin of ear opening and extend posteriorly to tail. Pale brown vertebral stripe two scale-rows wide. Five dark brown transverse bars between vertebral and dorsolateral stripe on each side. Gular region mostly black with about 10% of scales white, randomly scattered. Proximal dorsal surface of tail with four dark brown blotches on either side of midline; few blue scales scattered on proximal half.

Color in preservative. Dorsal and lateral surface of head brown; labials dark brown, bordered dorsally and ventrally by one row of white scales. Loreal scales white. Dorsum light brown, with dark brown transverse bars and light dorsolateral stripes as described above. All white regions on dorsum infused with blue (presumably from leeching). Lateral body scales light, with increasing melanism towards venter. Throat dark blue or black, with few, scattered light-colored scales. Venter dark blue and melanized, except for midventral, pale-colored patch about six scale-rows wide extending anteriorly from inguinal region, diminishing anteriorly until absent on chest. Dorsal surface of tail as above; ventral surface cream. Limbs same color as dorsum, with few scattered light blue scales.

Variation. Variation in meristic and mensural characters of male and female paratypes is summarized in Tables 3–4. All males have heavily mottled, dark turquoise throats. Ventral surfaces of two males (including the holotype) are similarly dark in preservative, with a distinct pale-colored patch extending midventrally from about the intersection of the hindlimbs towards the front limbs; in the third, the belly is much less melanized. The dorsal surface of males ranges from weakly patterned to patternless. In weakly patterned individuals, such as the holotype, the dark brown transverse bars between the vertebral and dorsolateral stripes are dimly evident. Figure 7 shows the coloration of an adult male in life; particularly noticeable are the orange-colored flanks of males. Of the two paratype females, one has a lightly mottled throat and ventral surface, while the other is pale. The dorsal surface of one female is strongly patterned, and marked with sharply defined dark transverse bars; the other female is patternless.

Comparisons. Sceloporus hesperus is one of the smallest species in the S. scalaris group, having a mean SVL of 45.4 mm. Sceloporus chaneyi , previously reported to be the smallest S. scalaris group species, has a mean SVL of 45.7 mm ( Liner & Dixon 1992). Sceloporus hesperus is most similar to S. subniger and S. dixoni , sharing with them a single canthal on each side of the head, relatively short legs (tibia length/head length proportion less than 0.9), small adult size (maximum SVL less than 63 mm), 36–50 dorsal scales, extensive dark pigment on the venter of adult males, a black-barred or darkly mottled chin/throat in adult males, orange or rust-colored flanks in adult males, and oviparity. Sceloporus hesperus can be distinguished from S. subniger by the combination of its smaller adult size (maximum SVL = 47 mm in S. hesperus vs. 62 mm in S. subniger ; average SVL = 45.4 mm vs. 48.6 mm), more dorsal scales (average of 43 vs. 41), more scales around midbody (average of 43 vs. 41), more ventral scales (average of 38 vs. 34), and fewer scales bordering the interpariatel scale (average of 14 vs. 16). Female S. hesperus also have considerably less mottling on the ventral surface than female S. subniger . Sceloporus hesperus differs from S. dixoni by the combination of their smaller adult size (maximum SVL = 47 mm in S. hesperus vs. 54 mm in S. dixoni ; average SVL = 45.4 mm vs. 47.1 mm), slightly shorter legs (average tibia length/head length proportion 0.84 vs. 0.86), more ventral scales (average = 38 vs. 35), more dorsal scales (41–47, average = 43 vs. 37–45, average = 41), and more scales around midbody (40–45, average = 43 vs. 37–43, average = 40).

Etymology. The specific epithet is derived from the Greek word hesperos, meaning “western”, and is used in reference to the type locality located at the far western end of the Trans-Mexican Volcanic Belt.

Distribution. Smith (1939: 356) cites several published records from the late 1800s for S. aeneus aeneus from Jalisco: “N of Rio Santiago ( Günther 1890); La Cumbre de los Arrastrados ( Boulenger 1897); Hda. Santa Gertrudis ( Boulenger 1897).” Over 50 years later, Smith et al. (1993: 133) commented that Boulenger’s records from Jalisco “appear to be too far west to be accepted without verification.” If Boulenger’s records are indeed correct, specimens from La Cumbre de los Arrastrados and Hacienda Santa Gertrudis in the Sierra de Cuale might be referable to S. hesperus . A narrow ridge above 2,200 m extends across southwestern Jalisco from the type locality in the Sierra de Mascota through the Sierra de Cuale to the Sierra de Manantlán. The reptiles and amphibians in this remote region of Mexico remain poorly sampled ( Reyes-Velasco et al. 2010). If suitable montane bunchgrass habitat is present along the forested mountain pass connecting these three sierras, then it is conceivable that additional populations of S. hesperus will be found here. For now, the only known population of S. hesperus is from the high-elevation pineoak forest at the type locality in the Sierra de Mascota of Jalisco. The low-elevation valleys trending northwest from the Nevado de Colima likely serve as a geographic barrier between S. hesperus and S. dixoni . This lower-elevation area is also inhabited by S. unicanthalis and S. scalaris ( Thomas & Dixon 1976; Watkins-Colwell et al. 2006), two larger-bodied species in the S. scalaris group not known to co-occur with S. subniger .

Figures

FIGURE 6. (A) Dorsal, (B) ventral, and (C) lateral views of the holotype of Sceloporus hesperus sp. nov. (MZFC 35571). (D) Close-up view of head.

FIGURE 7. Male Sceloporus hesperus sp. nov. from the type locality. Specimen photographed and released.